Apparatus for controlling moving members



April 2, 1963 R. 1.. CARLSTEDT 3,083,592

APPARATUS FOR CONTROLLING MOVING MEMBERS I Filed March 16, 1960 4Sheets-Sheet 1 vl/I KW r MA 5 m 7 W/ W n mdm m r H) %.W W a 7 A m z w 2v F L a WWW k 6 M O m HI q, M

April 2, 1963 R. L. CARLSTEDT 3,083,592

APPARATUS FOR CONTROLLING MOVING MEMBERS Filed March 16. 1960 4Sheets-Sheet 2 INVENTOR. 2/764 4/2 A. (wizsrffif April 2, 1963 R. L.CARLSTEDT 3,083,592

APPARATUS FOR CONTROLLING MOVING MEMBERS Filed March 16, 1960 4Sheets-Sheet 3 H 770/? NE 1 5 IN V EN TOR.

April 2, 1963 R. L. CARLSTEDT 3,083,592

APPARATUS FOR CONTROLLING MOVING MEMBERS Filed March 16. 1960 4Sheets-Sheet 4 INVENTOR.

46m? A. twain-fir Patented Apr. 2, 1963 3,Q83-,592 APPARATUS FURCGNTRGLLENG MOWG Ragnar L. (Zarlstedt, 27 Meade Road, Broad Axe, Ambler,Fa. Filed Mar. 16, 1969, Ser. No. 15,284 3 Claims. (til. 77-3) Thisinvention relates to an apparatus for controlling movements of movablemembers and is particularly concerned with the application of such amovement controlling device to the control of the movement of machinetool members and the like.

In machine tools relative movements between parts of the machine takeplace in order to carry out the work operations to be performed. Inturning and boring machines, for example, the part of the machinecarrying the cutting tool is moved relative to the part of the machinesupporting the workpiece so that feed movement of the cutting tool intothe workpiece can be obtained.

In other cases the movement of different members of a machine tool or alike organization are to be synchronized which might occur if, forexample, it was desired to move a press platen or the like inparallelism with itself while applying force to the platen at spacedpoints therealong. Heretofore, the exact control of such movements, orthe synchronization of such movements has been difficult and hasrequired the use of extremely expensive control equipment or acompromise between the results desired and the results that can heobtained practically.

With the foregoing in mind, it is a primary object of the presentinvention to provide an improved arrangement for effecting controls oftire nature referred to.

A still further object of the present invention is the provision of anarrangement for exactly controlling of the speed of a movable memberwhich has a driving force that is not in itself controlled.

A still i rther object of this invention is the provision of a motioncontrolling mechanism which is widely applicable to the control of themovement or" moving members regardless of the manner in which the memberis actuated.

It is also an object to provide a device for controlling the speed ofmovement of a reciprocating member in one direction wh le notinterfering in any way with the speed of movement of the member when itis moving in the opposite direction.

A particular object of this invention is the provision of a mechanismfor controlling the speed of movement of a hydraulically actuated memberwhich will in no way interfere with the operation of the hydraulicsystem.

i A still further object of this invention is the provision of a controlmechanism for regulating the speed of a moving object which will alsoserve to indicate changes in working condition of the moving member suchas would occur when a drill breaks through a workpiece or becomes dullor the like.

These and other objects and advantages will become more apparent uponreference to the drawings in which:

FIGURE 1 is a perspective view showing a deep hole boring machine of atype with which the present invention is particularly adaptable andhaving a control mechanism accordiri to this invention;

FIGURE 2 is a sectional view indicated by line 22 on FIGURE 1 showing,more or less diagrammatically, the construction of the control mechanismof the present invention;

FIGURE 3 is a view looking in at the left end of the machine of FIGURE 1as indicated by the line 3--3 on FIGURE 1;

FIGURE 4 is a diagrammatic representation of the hydraulic and electriccontrol circuit that can be used with the FIGURES 1 through 3modification;

FIGURE 5 is a view showing a modified construction for the nut and screwforming a part of this invention;

FIGURE 6 is a fragmentary view showing a modified arrangement forcontrolling the speed of rotation of the screw thereby to control thespeed of movement of the member to be controlled;

FIGURE 7 is a more or less diagrammatic view showing the application ofa control mechanism according to the present invention to an extremelylong bed machine;

FiGURE 8 is a section through the portion of the machine of FIGURE 7 inwhich the nut that cooperates with the control screw is located;

FlGURE 9 is a rather diagrammatic view showing a relatively long machineillustrating the manner in which an elongated control screw could besupported against bending;

FIGURE 10 is a sectional view indicated by line ill-id on FIGURE 9showing the screw and the supporting means therefor in cross section;

FIGURE 11 is a sectional view indicated by line llll on FIGURE 9 showingthe nut and the support therefor that cooperates with the screw;

FIGURE 12 is a view showing another manner in whch an elongated controlscrew could be supported against bending;

FIGURE 13 is a sectional view indicated by line 13-13 on FIGURE 12showing the construction of the shroud placed around the nut housing;

FlGURE i4 is a sectional view indicated by line 14-14 on FIGURE 12showing the construction of the means that supports the elongated screw;

FlGURE 15 is a sectional View showing a still other application of thecontrol device of the present invention in which the control device alsooperates to detect the dulling of a tool carried by the controlledmember;

FIGURE 16 is a sectional view drawn at enlarged scale through theportion of the device wherein the control referred to above is effected;

FIGURE 17 is a sectional view indicated by line l7l7 on FIGURE 15showing the construction support and drive for the nut that cooperateswith the control screw;

FEGURE 18 is a diagrammatic view showing the electrical and hydraulicactuating circuit of the FIGURE 15 modification; and

FIGURE 19 is a diagrammatic View showing an application of the controlmechanism of the present invention to a device other than the machinetool of the nature referred to above.

The present invention is concerned with a mechanism for controlling thespeed of movement of a member such as the tool slide or the like of amachine tool or similar mechanism. The present invention proposes toeffect such control by connecting between the member and another member,which may be stationary, relative to which the speed of the movablemembers to be controlled, a nut and screw so that the movement of themovable member can take place only as fast as the screw advances throughthe nut.

By controlling the rate of relative rotation between the screw and nut,the speed of movement of the movable member can be controlled withaccuracy. Usually, hydraulic means are employed to actuate the movablememher so that the nut and screw mechanism is required only to controlthe speed of movement of the member.

Usually, the speed control will be eilected in one direction of movementonly of the movable member and accordingly, the nut and screw arepreferably of the type in which either can drive the other wherebymovement of the movable member in the opposite direction can beaccomplished by high speed by permitting one or both of 3 the nut andscrew to spin freely while being driven by the other.

In another application of the control mechanism of the presentinvention, the control screw becomes extremely long on account of thelong travel that is being controlled, and in this case the screw issupported so that it does not sag and thus introduce inaccuracies orintroduce other problems such as buckling of the screw upon retractionof the control member.

Instill another embodiment of the present invention, spaced points of amember, or individual members are caused to move in unison or at apredetermined speed ratio to each other by providing each with a nut andscrew control mechanism according to this invention and interconnectingthe nuts and screws for movement in unison or at the desired speed ratiothereby synchronizing the movements of. the members controlled thereby.

Referring to the drawings now more in detail, FIG- URE 1 illustrates adeep hole boring machine in which there is a spindle 12 between whichand a clamp 14 there is. clamped a workpiece 16 which is driven inrotation by the spindle.

On the opposite side of the clamp 14 from workpiece 16 isaIreciprocab-le boring slide 18'which has mounted therein a boring toolor drill 20 that extends through the clamp into engagement with theworkpiece and which is advanced into the rotating workpiece by movementof the boring slide thereby to effect a boring or drilling operation. 7

The bring slide is connected to ram 22 of a hydraulic motor that alsoincludes a cylinder 24.

Reference to FIGURE 2 taken together with FIGURE 1 will'reveal that ram22 has a head 26 thereon forming a piston in cylinder 24 so that fluidcan be supplied to the advancing side of piston 26 by conduit 28 and tothe retractingside thereof by a conduit 30. l

' The piston and ram 22 are bored from the piston end and extendingtherein is a screw 32. 'This screw threads through a nut 34 rotatablymounted in the piston and supported therein on anti-friction bearingssuch as needle bearings 36. There is also a ball bearing at 38 whichbecomes effective when the piston is moving leftwardly and is exertingforce onthe nut. The left face of the nut is provided with a conicalclutch surface 44) adapted for cooperating with a complementary taperingclutch surface 42 formed in a plate 44 attached to .the piston; and

in addition to serving as a clutch plate, also retaining the nut in thepiston.

When the piston moves rightwardly, the aforementioned clutch faces 'willbe brought into engagement and will nonrotatably connect the nut withthe piston, whereas, when the piston moves leftwardly the nut comes intoengagement with hearing 38 and becomes rotatably connected with thepiston.

' Screw 32 extends, out through cylinder head 46 and is sealed theretoand .is rotatably supported therein by bearings48. V

Externally of the cylinder, screw 32 has rotatably mounted thereonasprocket 50 that is adapted for being drivingly engaged with a clutchmember 52 that is splined'to screw 32 as at 54. Movement of the clutchmember 52 into driving engagement with sprocket 50 is accomplished byspring 53 while energization of solenoid S1 will withdraw clutch member52 from the sprocket 59 and interrupt the driving connectiontherebetween.

As will be seen in FIGURES 1 and 3, there is a chain 56 passing aboutsprocket 5t) and leading over sprocket 58 driven by a motor 64). On whatis normally the slack side of the chain when the piston 26 and the ram22 are advancing rightwardly, there bears a roller 61 urged againstthechain by a spring 62. This roller 61 is mounted on an arm having aportion adjacent the operating plunger of a limit switch LS1. When thechain is slack on the roller side, the arm is spaced from the switch butwhen the slack side of the chain becomes 4 taut, the roller will belifted and the arm will actuate switch LS1. This can be availed of forindicating when the advance of the ram 22 slows down on account of thetool becoming dull or on account of there being a hard spot in theworkpiece or the like.

What occurs is that when the ram is advancing normally, the screw isunder tension and this tends to draw the lower reach of the chain tautwith the speed or rotation of motor 66 controlling the paying out of thechain thereby to controlthe speed of rotation of screw 32 thus to permitadvancing movement of ram 22 at the desired rate.

However, when the speed of movement of the'rarn is slowed down, thetension on the screw is relaxed and the condition at the chain changesfrom that wherein the lower reach of the chain is under tension andinstead the upper reach is under tension and this causes switch LS1 tobe actuated.

The speed-of rotation of the motor 60 can be efiected according to anyWell known means, such as a rheostat 64. Motor 60 could also be aconstant speed motor with there being a speed varying mechanism locatedbetween the output shaft of motor 60 and the sprocket 58 driven thereby.

A typical hydraulic and electric circuit for the modifi: cation ofFIGURES'l through 3 is illustrated in FIGURE 4. In FIGURE/4 the powerlines are indicated at L1 and L2 and therebetween is connected anormally open start switch 70 in series with the energizing coil of arelay R1 which includes a holding circuit in which there is a normallyclosed limit switch LS4 adapted for being opened by a cam member 72carried by boring slide 18 in its fully retracted position.

Relay RI when closed closes circuits through the valve solenoids A and Band through-the clutch solenoid S1 previously referred to.

Valve solenoid A pertains to a valve 74 which is normally'positioned toconnect conduit 28 leading'to the adv-ancing side of piston 26 to theexhaust conduit 76. Energization of solenoid A, however, shifts valve74- into position :to connect conduit 28 with pressure conduit'78leading to the discharge side of pump'8tl, and whichpres sure conduit iscontinuously connected to conduit 30 leading to the retraction side ofpiston 26.

Valve solenoid B is associated with a by-passvalveSZ which isnormally'open to by-pass the delivery of the pump back to reservoir 84but which, upon energization of solenoid B, closes to interrupt the saidby-pass.

In circuit with solenoid S1 pertaining to the clutch is a normallyclosed limit switch LS3 adapted for being opened by cam '72 when theboring slide reaches the position where it is desired for feed movementto commence.

speed. When switch LS3 is opened, however, and solenoid S1 isde-energized, clutch member 52 will move into engagement with sprocket50 thus commencing rotation of screw 32 at a controlled speed, wherebythe speed of advance of' the boring slide is regulated by the speed ofrotation of the screw.

When the boring slide advances to 'a point where'it will engage limitswitch LS2 "indicating that the feed 'movement has proceeded the desiredamount, the energizing coil for relay, R2 is energizedv and this relaycloses and holds'closed through a holding circuit that includes wire fieleading to switchLS4; Closing of relay R2 opens a blade 83 thereof sothat valve solenoid A is de-energi zed while solenoid B remainsenergized.

Valve 74 now shifts to exhaust the advancing'side of piston 26 so thepiston and the boring slide-connected therewith will move rapidly in theretracting direction.

Rapid movement is possible at this time because the nut' 34 isunclutched from clutch plate 44 and is free to spin in the piston sothat there is no restriction of the rate of movement of piston 26 andboring slide 18.

When the boring slide has reached its fully retracted position, switchLS4 will be opened and this will de-energize both relays R1 and R2 andthe system will come to rest with valve solenoid B being de-energizedand bypassing the entire delivery of pump 80 to reservoir 84.

In addition to relay R2 being energizable by closing of switch LS2, itcan also be energized by closing of the normally open manual switch 96should it be desired to initiate retraction manually, or it can beenergized by closing of the previously mentioned normally open switchLS1 when the advancing movement of the boring slide is slowed down as bythe cutting tool becoming dull or encountering hard spots in theworkpiece being operated.

While any accurately formed nut and screw can be utilized in thepractice of the present invention, and particularly nuts and screwswhich are mutually driveable by the other, I prefer to employ what isknown in the trade as a Saginaw screw, which is rather diagrammaticallyillustrated in FEGURE 5.

A screw of this nature has a thread 92 formed thereon which isessentially a half round ball bearing track and the nut 94 pertaining tothe screw has a track means for circulatin balls 95 which run in thetracl; 92. This makes for a very low friction free running arrangementwhich is ideally suited to the practice of the present invention.

In the modification of FIGURE 5, the nut 94 can be lined to the pistonand the screw permitted to turn so that durin" retraction movement it isthe screw which spins rather than the nut.

in the previously described modifications the control of the speed ofrotation of the screw has been eh'ected by a variable speed motor but itis also contemplated to control the speed of the screw by a governor orthe like as illustrated in .1 IGURE 6 thereby eliminating the necessityfor using a motor.

in FIGURE 6 bevel gears 98 connect the screw with a governor shaft 1%which carries the flyballs 192. When the fiyballs move outwardly againstthe bias of their springs tea, the plate 105 splined to shaft 1% movesupwadly and at a predetermined speed engages a brake plate 1% therebylimiting the speed of rotation of the screw.

Brake plate 1% is adjustable by screw threaded means lid to vary thesaid predetermined speed.

The arrangement of FIGURE 6 is directly applicable to the firstdescribed modification and can be made applicable to the FEGURE 5modification by including a clutch between the governor shaft and thecontrolled screw.

In FIGURES 7 and 8 there is shown a modification wherein the controlmechanism of the present invention is utilized for controlling the speedof movement of a member over a long distance while permitting the use ofa relatively short hydraulic motor to advance the member. This isaccomplished by attaching to the memher 112 which is to be controlled adouble acting ram 114 of a hydraulic motor that includes a cylinder 116.This motor is relatively short and the cylinder is mounted on a slide118 slidable on the machine bed 120. The slide also carries a motor 12?.connected by a chain 124 with a sprocket mounted on a shaft togetherwith a pinion 126 that engages a rack 128 attached to the bed 229. Thecylinder 116 is reversibly supplied with fluid from a pump 13d via asimple four-way reversing valve 132.

The member 112 has a rod 13 connected therewith having spaced cams 135and 38 adapted for engagement with a limit switch LS5 which, whenengaged by the cam 1% effects energization of the operating coil ofrelay R3 which has a holding circuit that includes a wire 1 extendingthrough the limit switch and which holding circuit is adapted for beinginterrupted when the limit switch is engaged by cam 138.

Relay R3 when energized closes the energizing circuit 5 to motor 122 tocause the motor to run in a direction to advance slide 11% toward member112.

Also associated with member 112 is the elongated threaded control rod142 which extends through the member and has disc like head 144 whichclutches rod 142 to the member when the member is pressing rightwardlyagainst head 144.

Threaded rod 142 extends through a stationary frame 145 within which, aswill be seen in FIGURE 8 there is a nut 148 threadedly engaging the rodand supported on anti-friction bearings 15% and having a sprocketportion 152 engaged by a chain driven by motor 154. It will be evidentthat advancing movement of member 112 can take place only as rapidly asnut 143 will permit the threaded rod 142 to move rightwardly. This, ofcourse, is determined by the speed of rotation of motor 154 which isvariable as by a rheostat, or as by a speed changing transmissionbetween the motor and the nut.

In operation, movement rightwardly of member 112 is commenced byshifting valve 132 to supply pressure fluid to the left side of doubleacting ram 114. With the ram so pressurized, rightward movement ofmember 112 will commence and at a rate determined by the speed ofrotation of nut 148. When member 312 is advanced rightwardly to thepoint that switch LS5 is actuated by cam 136, relay R3 will be energizedto bring about energization of motor 122 which will then drive slide H8toward member $12. Member 112, however, is constrained to move at thefixed predetermined rate determined by the speed of rotation of the nut148 and accordingly the rightward movement of slide 1 18 referred towill be accompanied by movement of cylinder 116 over double acting ram114- toward the right. The fluid displaced from the left end of cylinder116 during this movement can be by-passed back to reservoir 156 viapressure relief valve 158.

When the described movement of the slide all; toward member 112 hasbrought cam 3138 into engagement with switch LS5, relay R3 will bede-energized thus de-energizing motor 122 and bring the slide to a halt.

The aforementioned cycle will obtain repetitively until the desiredtotal travel of member 112 is executed.

It will be understood that de-energization of motor 122 will serve tolock slide 113 in place which could be accomplished as, for example,motor 122 being a geared head motor with self-locking worm gears betweenthe armature and the output shaft. it will also be understood automaticcontrols could be provided for limiting the total movement of member 112and for interrupting the movement at will or upon the tool 16% carriedthereby encountering more than a predetermined resistance. In any case,however, during the advancing movement of member 112, it will move at afixed rate of speed.

During retracting movement of member 112 it will merely slide overthreaded control rod 142, with the control rod being returned tostarting position by reversing of the drive means 154.

FIGURES 9 through 11 illustrate another long bed machine but in thismodification the movable member 17% is actuated by a hydraulic motor 172along enough to drive the motor directly throughout its travel.

The control screw or threaded rod 174 that regulates the rate ofmovement of slide 17%? is mounted in bed 17s of the machine is of suchlength that there is a possibility that it will sag and introduceinaccuracies and also introduce the possibility of buckling when slide17% returns. To eliminate the sagging of the screw it is arranged with atrough 1'78 in which there is a liquid 18%) of sufficient density tobuoy up the screw and support it against bending movement. Mercury, forexample, could be employed. The screw 174 may also be hollow asindicated in FIGURE 10 thus making it lighter and easier to support.

The nut 182 that runs on the screw is supported in a slide 17-1) byneedle bearings 184 with there being a ball bearing 1 86 that rotatablyconnects the nut with the FIGURES 12 through 14 modification the screw200 is supported by a plurality of blocks 2.02 which may be of plasticmaterial and which are attached to the upper side ofa flexible plastictube 204 positioned in trough 206 and retained therein between ribs 288'so as to float in liquid 210 in the trough thereby to support the screwagainst bending.

The nut onthe slide that the screw threadedly engages is provided with ashroud means 212 which-will depress the blocks 2G2 andtube'204 in theregion of the not as the slide'reciprocates whereby there is nointerference with the reciprocating movement of the slide.

FIGURES 15' through 18 show still, another modified arrangement of thepresent invention wherein means are provided for regulating the tensionon the screw during advancing movement of the controlled member.

In FIGURE 15 the movable member to be controlled,

is indicated at 220 and it is attached to double acting ram 222 of ahydraulic motor having a cylinder 224 into which extends a conduit 226to supply fluid to advance the ram and member and a conduit 228 whichsupplies fluid to the cylinder 224 for retracting the ram and memher.

The threaded control rod or screw 230 passes through a stationaryelement 232 and also through the member As will be seen in FIGURE 17within member 220 the screw t-hr'eadedly engages a nut. 234' thatcomprises a sprocket 236 driven by a chain 238 which in turn. is drivenby a power means 240. such asa motor.

With reference to member 232, aswill be seen in'FiG- URE 1'6, rod230iextends therethrough and at the rear of member 232 has attachedthereto a col1ar'24-2 that bearsagainst the outside of a cup 244. inwhich is a spring 246 urging the cup, collar, and threaded control rodrightwardly.

Cup 244 bears on a block 248 which is reciprocable in member 232' andurged toward the right by a'compression'spring 250, the bias of which isadjustable by nut.

252. It will be apparent that the support for the screw is such that itwill yield leftwardly under a predetermined high tension and will yieldrightwardly under a predetermined low tension. 7

These characteristics are availed of for controllingthe. tension exertedon the threadedirod so that it *canbe kept within predetermined limits;This is done by providing a normally open limit switch LS which isadapted for closing when block 248' moves leftwardly indicating that therod 230 is under apredetermined high tension.

Similarly, there is provided a normally closed limit switch LS7 which isadapted for being openedv when threaded rod 23:; moves rightwardlyindicating that it is being fed through nut 234 at a greater rate thanslide 220 is advancing.

The hydraulic and electrical control circuit in FIGURE 18 shows howthese switches are employed for control purposes.

In this figure it will be seen that the reversing valve 254 is connectedso that when the solenoid S2 is energized the valve will shift to supplypressure fluid to the advancing side of ram 224- to cause member 220 toad- Vance.

As the ram advances, the motor 240 which is energized simultaneouslywith solenoid S2 causes the nut 234 to rotate to feed screw 230 thuspermitting member 220 to advance at a predetermined rate.

During the advancing movement of member 22tiand ram 222 fluid fromtheretraction side of the ram isdischarged through a restrictor valve256. This valve has attached thereto an adjusting motor 258 which isIBVEI'Sl".

ble so that the degree of restriction of the valve can be varied.

If, during the advancing movement of member 220, r

the tension on screw 230 exceeds apredetermined'amount,

the screw will move leftwardly carrying'with it block 248 and this willpermit switch LSoto close on its contact 260 which willenergiz-e motor258 to run in a direction to increase the degree of restriction of valve256. This will cause more resistance to develop to the movement of ram222' and thus reduce the tension on screw 230. If, on the other hand,the tension on the screw is substantially less than the aforementionedtension, it will push the screw 239 rightwardly together with block 248toward its FIGURE 16 position and this will close limit switch LS6on'its contact 262 and cause motor 258 to run in the opposite directionthus decreasing the degree of.

restriction ofvalve 256 and decreasing the resistance to the advancingmovement of the ram 222.

In this manner the tension on the screw canbe maintained wi hinpredeterminedclose limits at all times.

Should the movement of the member 220 be slowed down or halted as bygoing against a stop, or by the tool carried thereby becoming dull, orthere being'a hard spot encountered in the workpiece being operated, thenot 234,

rotating on the screw, will drive the screw 230 to move rightwardly andto engage the open limit switch LS7 which will bring aboutde-energization of the control relay R3 which will de-energiz'e valvesolenoid S2 and thus cause the member 220 and ram 222 to retract.

Duringthis retracting movement nut 234, if disengaged from the drivemotor, may spin freely on screw 230, or it may disengage therefrom, ormotor 24%! maybe driven in the reverse direction;

The member 220 and ram 222 maybe caused to retract by operating manualswitch 270 ifso desired;'

A new cycle can be initiated at any time by closing start switch 272 toenergize relay R3 which will energize motor 240, valve solenoid S2, andestablish the energizing circuit'for motor 258.

, In the modification of FIGURE 19 there is shown an 7 arrangementwherein a single work member 300 or a pair of work members each haveconnected therewith the rams 362 and 364 respectively. Each rampertaining thereto has a control screw 306 threaded through a nut 308.The screws are interconnected externally of the cylinders in which therams are slideable by chain and sprocket means-310 so that the screwsare constrained to rotate at a predetermined speed ratio relativeto eachother.

' Any means for supplying pressure fluid to the opposite ends of therams-392 and 304 will result in the rams reciprocating in unison becausethey are positively locked together by the screws 396.

In the particular arrangement'illustrated .the lower ends of therams arehydraulically interconnected and are also connected'to an accumulator312 so that the member 300 will descend under load and will then raisein parallelism with itself as the load is reduced. This thus forms aconstant level platform for holding sheets of metal or the like atworking height.

The same arrangement, however, couldbe utilized forcontrolling theplaten of a press for a press brake or a shear to maintain the same inparallelism with itself.

In the several modifications referred to above there have been shownball bearing, nuts and screws, and other" substantially conventionaltypes of nuts, but it will be .understood that special collapsible nutscould be em- 9 ployed such as the half nuts used in the apron of a lathecarriage.

It is preferable for the nut to remain continuously in engagement withthe screw since no problems of reengagement are introduced but it willalso be evident that in many cases half nuts could be employed todisengage the screw entirely during the retracting movement and thatample opportunity would be available for reengaging the screw before itwas necessary for the nut to commence exercising the described control.

In all cases, the screw can be relatively small because the onlysubstantial loads thereon are those that are imposed on the screw intension with the screw being substantially unloaded during retraction ofthe controlled member.

It will be evident that in substantially every case the control of thespeed of the screw or nut could be accomplished in a number of ways,such as by a variable speed electric or hydraulic motor, or by variablespeed mechanical, hydraulic, or electrical transmissions connecting thedrive motor with the driven one of the screw and nut, or by adjustablegovernor means.

It will also be evident that while the present invention has beenparticularly illustrated and described in connection with controllingthe movable parts of machine tools, the same mechanism could be utilizedin any other circumstance in which it was desired accurately to controlthe speed of movement of a member or to retain the speed ratio betweentwo or more movable members.

It will be understood that this invention is susceptible to modificationin order to adapt it to different usages and conditions; and,accordingly it is desired to comprehend such modifications within thisinvention as may fall within the scope of the appended claims.

I claim:

1. In combination, a hydraulic motor comprising a cylinder and a ramtherein, said cylinder having a head at one end and said ram extendingout the other end thereof, a screw extending through the head of thecylinder and into the ram, a nut in the ram threaded on the screw, meansrotatably supporting the screw in the cylinder against axial movementtherein, a thrust bearing on one side of the nut between the nut and theram whereby movement of the ram in one direction in the cylinder willrotatably connect the nut with the ram, cooperating elements of a clutchbetween the other side of the nut and the ram whereby movement of theram in the other direction in the cylinder will non-rotatably connectthe nut with the ram, and means connected with the screw for controllingthe speed of rotation thereof at least while the ram is moving in thesaid other direction.

2. In combination, a hydraulic motor comprising a cylinder, 21 doubleacting ram in the cylinder extending from one end thereof, said cylinderhaving a head closing the other end thereof, a screw journaled in thecylinder head and extending into the ram, a cavity formed in the ram atthe screw end thereof, a nut on the screw in said cavity, a clutch platenon-rotatably mounted on the ram confining the nut in the cavity, saidclutch plate and nut having cooperating clutch surfaces thereon, saidclutch plate being operable for non-rotatably connecting the ram to thenut when the ram moves in a direction away from the head of the cylinderand thus moves the clutch plate against the nut and brings said clutchsurfaces into engagement, thrust bearing means between the nut and theram on the opposite side of the nut from said clutch plate whereby whenthe ram moves toward the head of the cylinder said nut is rotatablyconnected to the ram, and means connected with the screw for controllingthe speed of rotation thereof at least while the ram is moving away fromthe head of the cylinder.

3. In combination, a hydraulic motor comprising a cylinder, a headclosing one end of the cylinder, a ram reciprocable in the cylinder andextending from the other end thereof, a screw rotatably mounted in thehead of the cylinder and extending axially into the ram, a nut carriedby the ram threaded to the screw, said nut and screw being of thenon-self-flocking type, speed control means connected with the screw forcontrolling the speed of rotation thereof in one direction of movementof the ram in the cylinder, a clutch between said speed control meansand said screw disengageable while the ram is moving in the oppositedirection in the cylinder to permit the screw to spin freely, a clutchplate fixed to the ram on one side of the nut and said clutch plate andnut having cooperating clutch surfaces thereon, a thrust bearing betweenthe other side of the nut and the ram, and said nut having a smallamount of freedom of axial movement between said clutch plate and saidthrust bearing.

References Cited in the file of this patent UNITED STATES PATENTS2,367,492 Pickett et al. Jan. 16, 1945 2,529,753 Williams Nov. 14, 19502,587,352 Manning Feb. 26, 1952 2,601,157 Le Lan June 17, 1952 2,891,380Geyer et al. Jan. 23, 1959 2,958,232 Benninghoff et al. Nov. 1, 19602,994,305 Bruet Aug. 1, 1961

1. IN COMBINATION, A HYDRAULIC MOTOR COMPRISING A CYLINDER AND A RAMTHEREIN, SAID CYLINDER HAVING A HEAD AT ONE END AND SAID RAM EXTENDINGOUT THE OTHER END THEREOF, A SCREW EXTENDING THROUGH THE HEAD OF THECYLINDER AND INTO THE RAM, A NUT IN THE RAM THREADED ON THE SCREW, MEANSROTATABLY SUPPORTING THE SCREW IN THE CYLINDER AGAINST AXIAL MOVEMENTTHEREIN, A THRUST BEARING ON ONE SIDE OF THE NUT BETWEEN THE NUT AND THERAM WHEREBY MOVEMENT OF THE RAM IN ONE DIRECTION IN THE CYLINDER WILLROTATABLY CONNECT THE NUT WITH THE RAM, COOPERATING ELEMENTS OF A CLUTCHBETWEEN THE OTHER SIDE OF THE NUT AND THE RAM WHEREBY MOVEMENT OF THERAM IN THE OTHER DIRECTION IN THE CYLINDER WILL NON-ROTATABLY CONNECTTHE NUT WITH THE RAM, AND MEANS CONNECTED WITH THE SCREW FOR CONTROLLINGTHE SPEED OF ROTATION THEREOF AT LEAST WHILE THE RAM IS MOVING IN THESAID OTHER DIRECTION.